78 lines
2.5 KiB
Haskell
78 lines
2.5 KiB
Haskell
-- requires cabal install --lib megaparsec parser-combinators
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module Main (main) where
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import Control.Monad (void, when)
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import Data.Char qualified as C
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import Data.Functor
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import Data.List qualified as L
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import Data.Map qualified as M
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import Data.Maybe
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import Data.Set qualified as S
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import Data.Void (Void)
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import Text.Megaparsec
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import Text.Megaparsec.Char
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exampleExpectedOutput = 281
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type Input = [(Int, Int)]
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type Parser = Parsec Void String
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parseDigit :: Parser Int
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parseDigit = (C.digitToInt <$> digitChar)
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<|> (string "one" $> 1)
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<|> (string "two" $> 2)
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<|> (string "three" $> 3)
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<|> (string "four" $> 4)
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<|> (string "five" $> 5)
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<|> (string "six" $> 6)
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<|> (string "seven" $> 7)
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<|> (string "eight" $> 8)
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<|> (string "nine" $> 9)
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<|> (letterChar *> parseDigit)
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parseDigitReversed :: Parser Int
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parseDigitReversed = (C.digitToInt <$> digitChar)
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<|> (string "eno" $> 1)
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<|> (string "owt" $> 2)
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<|> (string "eerht" $> 3)
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<|> (string "ruof" $> 4)
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<|> (string "evif" $> 5)
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<|> (string "xis" $> 6)
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<|> (string "neves" $> 7)
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<|> (string "thgie" $> 8)
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<|> (string "enin" $> 9)
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<|> (letterChar *> parseDigitReversed)
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parseFirstAndLast :: String -> (Int, Int)
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parseFirstAndLast str = (f, l)
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where
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f = case runParser parseDigit "parseDigit" str of
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Left bundle -> error $ errorBundlePretty bundle
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Right input' -> input'
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l = case runParser parseDigitReversed "parseDigit" (reverse str) of
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Left bundle -> error $ errorBundlePretty bundle
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Right input' -> input'
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parseInput' :: Parser Input
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parseInput' = fmap parseFirstAndLast <$> some (some alphaNumChar <* eol) <* eof
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parseInput :: String -> IO Input
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parseInput filename = do
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input <- readFile filename
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case runParser parseInput' filename input of
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Left bundle -> error $ errorBundlePretty bundle
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Right input' -> return input'
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process :: Int -> (Int, Int) -> Int
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process acc l = acc + fst l * 10 + snd l
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compute :: Input -> Int
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compute = L.foldl' process 0
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main :: IO ()
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main = do
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example <- parseInput "example2"
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let exampleOutput = compute example
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when (exampleOutput /= exampleExpectedOutput) (error $ "example failed: got " ++ show exampleOutput ++ " instead of " ++ show exampleExpectedOutput)
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input <- parseInput "input"
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print $ compute input
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